The claimed systems and methods relate generally to loudspeaker teleconferencing systems that utilize echo cancellation and full duplex operation with distant participants, and more particularly to teleconferencing systems that implement narrow-band doubletalk detectors, secondary modes of doubletalk detection and partial mixing of audio between two far-end participants or one far-end participant and a local audio source.
The reader is referred to the following U.S. patents for background information. U.S. Pat. No. 5,933,495 to Oh describes a subband acoustic echo canceller that includes the freezing of filter coefficients on detection of near-end speech. U.S. Pat. No. 5,937,060, also to Oh, describes a residual echo suppression system in connection with an echo canceller. U.S. Pat. No. 6,990,194 to Mikesell et al. describes the use of sub-banded voice activity detectors coupled to an echo cancelling circuit. All of these references are hereby incorporated by reference as background material for the description that proceeds below.